Silicon cation and anion chemistry in a fuel-rich, methane–oxygen flame

1992 ◽  
Vol 70 (4) ◽  
pp. 1069-1081 ◽  
Author(s):  
J. Hugh Horton ◽  
John M. Goodings
Keyword(s):  
Nucleophilic Substitution ◽  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Orthosilicic Acid ◽  
Ion Chemistry ◽  
Silicon Ions ◽  
Normal Carbon ◽  
Silicon Chemistry ◽  
Three Body ◽  
Oxygen Flame

Silicon cations and anions in a fuel-rich, premixed, methane–oxygen flame at atmospheric pressure doped with 0.01 mol% of trimethylsilane were observed by sampling the flame through a nozzle into a mass spectrometer. Twelve cations were observed which can be grouped into five series: SiOH+.nH2O (n = 0–2); SiOCH3+.nH2O (n = 0–2); Si(OH)3+.nH2O (n = 0–2); cations by nucleophilic substitution (e.g., Si(OH)(CH3)2(H2O)+); and carbonaceous aromatic cations (c-HSiCH=CH+ and c-HSiCH=CCH3+). Similarly, five anions were observed as members of two series: HxSiO3− (x = 0, 1) and HxSiO4− (x = 1–3). The chemical ionization reactions for the formation of these ions are discussed in detail, including proton transfer and also methyl cation transfer, three-body addition, nucleophilic substitution (SN2) of both the ions themselves and also their neutral silicon precursors, and H-atom abstraction reactions. The neutral silicon chemistry in the flame is dominated by SiO, but evidence was obtained from both the cation and the anion chemistry for the presence of HSiO(OH), silanoic acid; SiO(OH)2, metasilicic acid; and Si(OH)4, orthosilicic acid. The silicon ion chemistry differs markedly from the normal carbon ion chemistry that occurs naturally in the undoped methane–oxygen flame; the silicon ions show a strong tendency towards Si—O bond formation. Consideration is given to the probable structures of the various silicon cations and anions observed.

Ion chemistry of second-row transition metals in hydrocarbon flames: cations and anions of Y, Zr, Nb, and Mo

1995 ◽  
Vol 73 (12) ◽  
pp. 2263-2271 ◽  
Author(s):  
Christine C.Y. Chow ◽  
John M. Goodings
Keyword(s):  
Transition Metals ◽  
Gas Phase ◽  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Ion Concentration ◽  
Oxidation States ◽  
Metallic Ions ◽  
Ion Chemistry ◽  
Hydrocarbon Flames

A pair of laminar, premixed, CH4–O2 flames above 2000 K at atmospheric pressure, one fuel-rich (FR) and the other fuel-lean (FL), were doped with ~10−6 mol fraction of the second-row transition metals Y, Zr, Nb, and Mo. Since these hydrocarbon flames contain natural ionization, metallic ions were produced in the flames by the chemical ionization (CI) of metallic neutral species, primarily by H3O+ and OH− as CI sources. Both positive and negative ions of the metals were observed as profiles of ion concentration versus distance along the flame axis by sampling the flames through a nozzle into a mass spectrometer. For yttrium, the observed ions include the YO+•nH2O (n = 0–3) series, and Y(OH)4−. With zirconium, they include the ZrO(OH)+•nH2O (n = 0–2) series, and ZrO(OH)3−. Those observed with niobium were the cations Nb(OH)3+ and Nb(OH)4+, and the single anion NbO2(OH)2−. For molybdenum, they include the cations MoO(OH)2+ and MoO(OH)3+, and the anions MoO3− and MoO3(OH)−. Not every ion was observed in each flame; the FL flame tended to favour the ions in higher oxidation states. Also, flame ions in higher oxidation states were emphasized for these second-row transition metals compared with their first-row counterparts. Some ions written as members of hydrate series may have structures different from those of simple hydrates; e.g., YO+•H2O = Y(OH)2+ and ZrO(OH)+•H2O = Zr(OH)3+, etc. The ion chemistry for the production of these ions by CI in flames is discussed in detail. Keywords: transition metals, ions, flame, gas phase, negative ions.

Comparative sulphur cation chemistry in a hydrocarbon flame with H2S, OCS, and SO2 additives

1986 ◽  
Vol 64 (12) ◽  
pp. 2412-2417 ◽  
Author(s):  
Nicholas S. Karellas ◽  
John M. Goodings
Keyword(s):  
Reaction Zone ◽  
Atmospheric Pressure ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Mass Range ◽  
Total Ionization ◽  
Ion Recombination ◽  
Diffusion Mass ◽  
Oxygen Flame

A fuel-rich, conical, premixed, methane–oxygen flame at atmospheric pressure was doped separately with 0.2 mol% of H2S, OCS, and SO2 to probe the chemistry of sulphur at its source during combustion. These three additives represent a broad range of fuel-sulphur contaminants since they occur early, intermediate, and late in the sulphur oxidation sequence. A wide variety of sulphurous cations, formed by chemical ionization reactions, is observed for each additive by sampling the flame into a mass spectrometer. The total ionization profile measured along the flame axis is enhanced in the reaction zone when a sulphur additive is present; the mechanism involves the formation of sulphurous negative ions which reduces the rates of cation loss by electron–ion recombination and ambipolar diffusion. Mass spectra measured in the mass range 10–110 u at fixed points on the flame axis are very similar for all three additives, and are not helpful in the identification of the additive. However, the general presence of sulphur is evident from large signals measured near the reaction zone at five principal mass numbers; namely, 45 u (CHS+), 47 u (CH3S+), 58 u (C2H2S+), 59 u (C2H3S+), and 69 u (C3HS+) related to CS, thioformaldehyde, thioketene, and C3S.

scholarly journals Multi-scheme chemical ionization inlet (MION) for fast switching of reagent ion chemistry in atmospheric pressure chemical ionization mass spectrometry (CIMS) applications

2019 ◽  
Author(s):  
Matti P. Rissanen ◽  
Jyri Mikkilä ◽  
Siddharth Iyer ◽  
Jani Hakala
Keyword(s):  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Atmospheric Pressure Chemical Ionization ◽  
Sample Pretreatment ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Reaction Products ◽  
Ion Chemistry ◽  
Fast Switching ◽  
Pressure Chemical Ionization

Abstract. A novel chemical ionization inlet (Multi-scheme chemical IONization inlet, MION, Karsa Ltd, Helsinki, Finland) capable of fast switching between multiple reagent ion schemes is presented and its performance is demonstrated by measuring several known oxidation products from much studied cyclohexene and α-pinene ozonolysis systems, by applying consecutive bromide (Br−) and nitrate (NO3−) chemical ionization. Experiments were performed in flow tube reactors under atmospheric pressure and room temperature (22 °C) utilizing atmospheric pressure interface time-of-flight mass spectrometer (APi-ToF-MS, Tofwerk Ltd, Thun, Switzerland) as the detector. The application of complementary ion modes in probing the same steady-state reaction mixture enabled a far more complete picture of the detailed autoxidation process; the HO2 radical and the least oxidized reaction products were retrieved with Br− ionization, whereas the highest oxidized reaction products were detected in the NO3− mode, directly informing on the first steps and on the ultimate end-point of oxidation, respectively. While chemical ionization inlets with multiple reagent ion capabilities have been reported previously, an application in which the charging of the sample occurs at atmospheric pressure with practically no sample pretreatment, and with the potential to switch the reagent ion scheme within a second time-scale, has not been introduced previously. Also, the ability of bromide ionization to detect highly-oxygenated organic molecules (HOM) from atmospheric autoxidation reactions has not been demonstrated prior to this investigation.

scholarly journals Multi-scheme chemical ionization inlet (MION) for fast switching of reagent ion chemistry in atmospheric pressure chemical ionization mass spectrometry (CIMS) applications

2019 ◽  
Vol 12 (12) ◽  
pp. 6635-6646 ◽  
Author(s):  
Matti P. Rissanen ◽  
Jyri Mikkilä ◽  
Siddharth Iyer ◽  
Jani Hakala
Keyword(s):  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Atmospheric Pressure Chemical Ionization ◽  
Sample Pretreatment ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Reaction Products ◽  
Ion Chemistry ◽  
Fast Switching ◽  
Pressure Chemical Ionization

Abstract. A novel chemical ionization inlet named the Multi-scheme chemical IONization inlet (MION), Karsa Ltd., Helsinki, Finland) capable of fast switching between multiple reagent ion schemes is presented, and its performance is demonstrated by measuring several known oxidation products from much-studied cyclohexene and α-pinene ozonolysis systems by applying consecutive bromide (Br−) and nitrate (NO3-) chemical ionization. Experiments were performed in flow tube reactors under atmospheric pressure and room temperature (22 ∘C) utilizing an atmospheric pressure interface time-of-flight mass spectrometer (APi-ToF-MS, Tofwerk Ltd., Thun, Switzerland) as the detector. The application of complementary ion modes in probing the same steady-state reaction mixture enabled a far more complete picture of the detailed autoxidation process; the HO2 radical and the least-oxidized reaction products were retrieved with Br− ionization, whereas the highest-oxidized reaction products were detected in the NO3- mode, directly providing information on the first steps and on the ultimate endpoint of oxidation, respectively. While chemical ionization inlets with multiple reagent ion capabilities have been reported previously, an application in which the charging of the sample occurs at atmospheric pressure with practically no sample pretreatment, and with the potential to switch the reagent ion scheme within a second timescale, has not been introduced previously. Also, the ability of bromide ionization to detect highly oxygenated organic molecules (HOM) from atmospheric autoxidation reactions has not been demonstrated prior to this investigation.

Sign in / Sign up

Export Citation Format

Share Document